Rainbow Dash finds a new shop in town that sells all sorts of rare items. All the shopkeeper asks in return is that you sell of something of yours in return. Soon it becomes Ponyville's biggest new talking point, as ponies weigh up exactly what they'd consider loosing in return for fulfilling their hearts desires.
A silly, largely SFW story that deals with modularity, aka detachable body parts. Full on cartoon logic for most of it. May include NSFW chapters as side stories that are basically "non canon"